In semiconductor manufacture technologies, a widely known method for electrically connecting a semiconductor chip to a conductor pattern (referred to below as a conductor lead) in which a semiconductor chip is formed on a lead frame or an insulating substrate, is a method using super fine wire bonding (including the thermocompression bonding method, the ultrasonic method, the thermosonic method in which the above-mentioned two methods are combined, etc.). During wire bonding, one end of gold (Au) and other super fine wires are bonded to electrode pads on the circuit forming surface of a semiconductor chip by a capillary tool and looped, that is, arranged so that they form loops. The other ends are bonded to the conductor leads.
One advantage of wire bonding is that mutual shrinkage between internal members of a semiconductor device due to heat is absorbed by the flexibility of the wires, so that high connection reliability is obtained. On the other hand, the flexibility of the wires is disadvantageous because short circuits between the wires can be generated when a molding resin is poured. Along with the demand for miniaturization and high performance of semiconductor devices, the number of wires per unit area has increased, and the short circuit problem between the wires becomes more serious when the molding resin is poured.
FIG. 9 is a conceptual diagram showing a resin flow in a mold 30 based on a transfer molding method. A melted molding resin is poured into a cavity 34 for forming semiconductor devices 10 and 20 shown in FIGS. 1 and 6 from a gate 31 arranged at the corner. The molding resin flows from the corner where the gate 31 is arranged into the cavity 34 and toward the corner 35 that is diagonally opposite the gate. Here, since wires 32 extend radially from the electrode pads arranged around the semiconductor chip 33 in all directions, some wires, that is, the wires in the corners 34' in the cavity 34 on both sides of the gate receive the flow of the molding resin from an approximately perpendicular direction.
FIGS. 10 and 11 are enlarged diagrams showing one of the two side corners 34' in the cavity that receive a flow of molding resin that is approximately perpendicular to the wires 32 when the resin is poured from position A in FIG. 9, that is, the above-mentioned gate 31. The two figures show the condition before and after the molding resin is poured. As shown in the figure, a conventional semiconductor device has the area 34 at the corner of the semiconductor chip 33, where there is no electrode pad 33a. After a semiconductor device has been sealed with a molding resin, mechanical stresses are generated in a region with a size of about 200-400 .mu.m in the corner (33') of semiconductor chip (33), and cracks are generated in the silicon that is used as the substrate for the semiconductor chip 33 or connection defects are generated in the wire 32, so that the reliability is lowered. For this reason, this design is disadvantageous for I/O buffer circuits, antistatic circuits (ESD circuits), electrode pads, etc. Therefore, as shown in the figure, the gap between the two closest wires 32a and 32b in the corner (33') of the semiconductor chip is wider than the gap between the other wires.
As shown in FIG. 11, the arrow shows the direction of the flow of the molding resin poured from gate 31, in the two corners 34', which are toward the sides with respect to the gate position of the cavity 34, and the flow is approximately perpendicular to the direction of the wires 32. The wires 32 resist the flow of the molding resin but the gap between the wires 32a and 32b in the two side corners in the cavity 34 is widened as mentioned above, so that the resistance is decreased, thereby accelerating the flow. For this reason, the wire 32b, which is downstream of this gap, receives a larger force and is largely deformed, so that the risk of short circuits with adjacent wires is increased.
Therefore, the purpose of the present invention is to prevent wires at the corner of a semiconductor chip from contacting adjacent wires due to the flow of a molding resin, that is, to prevent the short circuit of wires. Another purpose of the present invention is to prevent the short circuit of the above-mentioned adjacent wires with little change to the structure and the manufacturing processes of a semiconductor device.